This disclosure relates to a mid-turbine frame buffer system for a gas turbine engine.
A mid-turbine frame is a structural case that is used to support the aft end of the high spool shaft of a turbofan engine. The mid-turbine frame is located between the high pressure turbine and low pressure turbine, a location where the core flowpath pressure and temperature are high. The static mid-turbine frame supports a rotating high speed shaft through a bearing enclosed in a buffered bearing compartment. Since the bearing must be cooled and lubricated with a constant oil flow, seals are used to contain the oil at static-to-rotating interfaces. The buffer air pressure outside of the bearing compartment must remain higher than the pressure inside the compartment so that air always leaks into the compartment, not out, so that the oil is contained within the bearing compartment.